[sdiy] stuck on TR-909 hats repair

[epk]

Hey all,

I was poking around grounding the address pins that drive the hihat  
rom and I seem to have damaged something (D'oh! forgot the pullup  
resistor).  The audio directly off the D/A sounds like it's bit  
reduced, so on the advice of a friend I bought a logic probe and sure  
enough one of the bits (pin 15 on IC 68) is always low.  I get some  
activity on the input (pin 14) of that flipflop although the tone  
from the logic probe is different than the other 5 pins.

In the circuit pre D/A, I've replaced all the IC's (except for the  
rom), replaced all the transistors, and tested all the caps, diodes,  
and resistors.  Aside from replacing the rom I don't know what to do  
next.

This was literally the last thing I had to finish before project  
completion, so I'm pretty bummed about it....any suggestions or  
insight is much appreciated!

Thanks,

epk